Electron beam exposure apparatus and its control method

ABSTRACT

An electron beam exposure apparatus for drawing a pattern on an object to be exposed using a plurality of electron beams. The apparatus includes an electron beam source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed and an adjustment unit for dynamically adjusting sizes of dot patterns formed on the object to be exposed upon projection of the intermediate images in correspondence with fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.

This application is a divisional of application Ser. No. 09/082,324,filed May 21, 1998 now U.S. Pat. No. 6,107,636.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electron beam exposure apparatusand, more particularly, to an electron beam exposure apparatus fordrawing a pattern on a wafer or drawing a pattern on a mask or reticleusing a plurality of electron beams, and its control method.

2. Description of the Related Art

An electron beam exposure apparatus includes a point beam type apparatuswhich uses a beam shaped in a spot pattern, a variable rectangular beamtype apparatus which uses a beam shaped to have a rectangular sectionwith a variable size, a stencil mask type apparatus which shapes a beaminto a desired sectional shape using a stencil, and the like.

The point beam type electron beam exposure apparatus is used for onlyresearch purposes due to its low throughput. The variable rectangularbeam type electron beam exposure apparatus has a throughput higher byone or two orders of magnitude than that of the point beam type, butsuffers problems in terms of throughput when highly integrated patternshaving a line width as small as about 0.1 μm are to be formed byexposure. on the other hand, the stencil mask type electron beamexposure apparatus uses a stencil mask formed with a plurality ofrepetitive pattern through holes in a portion corresponding to avariable rectangular aperture. Hence, the stencil mask type electronbeam exposure apparatus is effective for exposure of repetitivepatterns. However, when a semiconductor circuit requires a large numberof transfer patterns that cannot be formed on a single stencil mask, aplurality of stencil masks must be prepared in advance, and must be usedone by one, resulting in a long mask exchange time and a considerablethroughput drop.

As an apparatus that can solve the above problems, a multi-electron beamtype exposure apparatus is known. In this apparatus, a plurality ofelectron beams are irradiated.on the sample surface along the course ofdesign coordinate positions, and are deflected along that course ofdesign coordinate positions to scan the sample surface. In addition, theplurality of electron beams are individually ON/OFF-controlled incorrespondence with the pattern to be drawn, thereby drawing thepattern. Since the multi-electron beam type exposure apparatus can drawan arbitrary pattern, it can improve the throughput.

FIG. 15A schematically shows the multi-electron beam type exposureapparatus. Reference numerals 501 a, 501 b, and 501 c denote electronguns that can individually ON/OFF-control electron beams. Referencenumeral 502 denotes a reduction electron optical system for projecting aplurality of electron beams emitted by the electron guns 501 a, 501 b,and 501 c onto a wafer 503 in a reduced scale; and 504, a deflector fordeflecting the plurality of electron beams to be projected onto thewafer 503 in the reduced scale.

The plurality of electron beams coming from the electron guns 501 a, 501b, and 501 c are deflected by an identical amount by the deflector 504.With this deflection, the respective electron beams are deflected whilesequentially settling their positions on the wafer in accordance with amatrix having a matrix spacing defined by the minimum deflection widthof the deflector 504 with reference to their beam reference positions.The individual electron beams form exposure patterns. on differentexposure regions by exposure.

FIGS. 15B to 15D show the state wherein the electron beams coming fromthe electron guns 501 a, 501 b, and 501 c expose the correspondingexposure regions to form exposure patterns in accordance with anidentical matrix. The respective electron beams move while settlingtheir positions on the matrix at the same time like (1, 1), (1, 2), . .. , (1, 16), (2, 1), (2, 2), . . . , (2, 16), (3, 1), . . . , and exposethe corresponding regions to form patterns (P1, P2, P3) by turning onthe beams at the positions of the exposure patterns (P1, P2, P3).

In the multi-electron beam type exposure apparatus, since the respectivebeams simultaneously form different patterns, the size of each electronbeam and the minimum deflection width of the deflector 504 correspondingto that size are set in correspondence with the minimum line width ofthe exposure patterns. As the minimum line width becomes smaller, thenumber of times of exposure while settling the electron beam positionsincreases, resulting in a considerable throughput drop.

The exposure patterns do not always equally include patterns with aminimum line width. However, conventionally, even in a region defined bya pattern having a line width larger than the minimum line width,exposure is done using the electron beam size and the minimum deflectionwidth corresponding to that size, determined based on the minimum linewidth in all the patterns. For this reason, the throughput drops as theminimum line width of the pattern shrinks.

SUMMARY OF THE INVENTION

It is an object of the present invention to achieve high throughput bydynamically changing the dot pattern size to be formed on the object tobe exposed upon forming a single pattern by exposure.

An electron beam exposure apparatus according to one aspect of thepresent invention is an electron beam exposure apparatus for drawing apattern on an object to be exposed using a plurality of electron beams,comprising an electron source for emitting electrons, a plurality ofelementary electron optical systems for respectively formingintermediate images of the electron source, a projection electronoptical system for projecting the plurality of intermediate images ontothe object to be exposed and an adjustment unit for dynamicallyadjusting sizes of dot patterns formed on the object to be exposed uponprojection of the intermediate images in correspondence with fields tobe exposed of the pattern to be drawn by exposure on the object to beexposed.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts the sizes of the intermediate images to be projected onto theobject to be exposed, thereby dynamically adjusting the sizes of the dotpatterns to be formed on the object to be exposed.

The electron beam exposure apparatus further comprises an illuminationelectron optical system which is inserted between the electron sourceand the plurality of elementary electron optical systems, and is adaptedto convert the electrons emitted by the electron source intosubstantially collimated electron beams, and to irradiate the electronbeams onto the plurality of elementary electron optical systems, andwherein the adjustment unit adjusts the focal length of the illuminationelectron optical system to adjust the sizes of the intermediate imagesto be projected onto the object to be exposed.

In the electron beam exposure apparatus, the adjustment unit adjusts thefocal length of the illumination optical system while fixing a focalpoint position of the illumination electron optical system on theelectron source side.

In the electron beam exposure apparatus, the illumination electronoptical system comprises a plurality of electron lenses disposed in anoptical axis direction, and the adjustment unit adjusts the focal lengthof the illumination electron optical system while fixing the focal pointposition of the illumination electron optical system on the electronsource side, by changing focal lengths of at least two of the pluralityof electron lenses.

The electron beam exposure apparatus further comprises an axiscorrection unit for correcting position deviations of the intermediateimages to be projected onto the object to be exposed produced when theadjustment unit adjusts the focal length of the illumination electronoptical system.

In the electron beam exposure apparatus, the axis correction unitcorrects the position deviations of the intermediate images of theelectron source to be projected onto the object to be exposed bycorrecting positions of the plurality of intermediate images formedimmediately below the plurality of elementary electron optical systems.

The electron beam exposure apparatus further comprises a scanning unitfor scanning the intermediate images to be projected onto the object tobe exposed, and wherein the adjustment unit dynamically adjusts aminimum scanning width of the scanning unit in correspondence with thesizes of the dot patterns to be formed on the object to be exposed.

In the electron beam exposure apparatus, the scanning unit comprises adeflector for deflecting electron beams to be irradiated from theplurality of elementary electron optical systems onto the object to beexposed, and the adjustment unit dynamically adjusts a minimumdeflection width of the deflector in correspondence with the sizes ofthe dot patterns to be formed on the object to be exposed.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts a scanning cycle of the scanning unit in correspondence with theminimum scanning width of the scanning unit.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts a deflection cycle of the scanning unit in correspondence withthe minimum deflection width of the deflector.

In the electron beam exposure apparatus, the plurality of elementaryelectron optical systems have a function of correcting any aberrationsproduced upon projecting the plurality of intermediate images formed bythe plurality of elementary electron optical systems onto the object tobe exposed via the projection electron optical system.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts the sizes of the dot patterns to be formed on the object to beexposed by projecting the intermediate images in accordance with a unitexposure field to be exposed of the entire field of the pattern to bedrawn by exposure on the object to be exposed, the entire field beingmade up of a set of a plurality of unit exposure fields.

In the electron beam exposure apparatus, the adjustment unit adjusts thesizes of the dot patterns to be formed on the object to be exposed byprojecting the intermediate images in units of unit exposure fields onthe basis of a feature of an exposure pattern in the corresponding unitexposure field.

In the electron beam exposure apparatus, the adjustment unit adjusts thesizes of the dot patterns to be formed on the object to be exposed byprojecting the intermediate images in units of unit exposure fields onthe basis of a minimum line width of an exposure pattern in thecorresponding unit exposure field.

According to another aspect of the present invention, an electron beamexposure apparatus for drawing a pattern on an object to be exposedusing a plurality of electron beams, comprises an electron source foremitting electrons, a projection electron optical system for projectingan image of the electron source onto the object to be exposed, and anadjustment unit for dynamically adjusting a size of a dot pattern formedon the object to be exposed upon projection of the image of the electronsource in correspondence with fields to be exposed of the pattern to bedrawn by exposure on the object to be exposed.

According to still another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronsource for emitting electrons, a plurality of elementary electronoptical systems for respectively forming intermediate images of theelectron source, and a projection electron optical system for projectingthe plurality of intermediate images onto the object to be exposed,comprises the step of dynamically adjusting sizes of dot patterns formedon the object to be exposed upon projection of the intermediate imagesin correspondence with fields to be exposed of a pattern to be drawn byexposure on the object to be exposed.

According to still another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronsource for emitting electrons, and a projection electron optical systemfor projecting an image of the electron source onto the object to beexposed, comprises the step of dynamically adjusting a size of a dotpattern formed on the object to be exposed upon projection of the imageof the electron source in correspondence with fields to be exposed of apattern to be drawn by exposure on the object to be exposed.

According to still another aspect of the present invention, a method ofgenerating exposure control data used for controlling an electron beamexposure apparatus, which has an electron source for emitting electrons,a plurality of elementary electron optical systems for respectivelyforming intermediate images of the electron source, and a projectionelectron optical system for projecting the plurality of intermediateimages onto the object to be exposed, comprises the steps of dividing apattern to be drawn by exposure on the object to be exposed into aplurality of blocks, detecting features of patterns in the blocks,determining sizes of dot patterns to be formed on the object to beexposed by projecting the intermediate images in units of blocks on thebasis of the features of the patterns in the blocks, and generatingexposure control data on the basis of the determination result.

It is another object of the present invention to achieve high throughputby dynamically changing the minimum scanning width for scanning anintermediate image on the object to be exposed upon forming a singlepattern by exposure.

An electron beam exposure apparatus according to one aspect of thepresent invention is an electron beam exposure apparatus for drawing apattern on an object to be exposed using a plurality of electron beams,comprising an electron source for emitting electrons, a plurality ofelementary electron optical systems for respectively formingintermediate images of the electron source, a projection electronoptical system for projecting the plurality of intermediate images ontothe object to be exposed, a scanning unit for scanning the plurality ofintermediate images to be projected onto the object to be exposed, andan adjustment unit for dynamically adjusting a minimum scanning width ofthe scanning unit in correspondence with fields to be exposed of thepattern to be drawn by exposure on the object to be exposed.

In the electron beam exposure apparatus, the scanning unit comprises adeflector, and the adjustment unit dynamically adjusts a minimumdeflection width of the deflector in correspondence with the fields tobe exposed of the pattern to be drawn by exposure on the object to beexposed.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts the minimum scanning width of the scanning unit in accordancewith a unit exposure field to be exposed of the entire field of thepattern to be drawn by exposure on the object to be exposed, the entirefield being made up of a set of a plurality of unit exposure fields.

In the electron beam exposure apparatus, the adjustment unit adjusts theminimum scanning width of the scanning unit, to a minimum scanning widthdetermined based on a minimum line width of an exposure pattern in thecorresponding unit exposure field, in units of unit exposure fields.

In the electron beam exposure apparatus, the adjustment unit controlsthe scanning unit to scan electron beams without settling the electronbeams in correspondence with a field, where none of the intermediateimages are projected, i.e., no electron beams are irradiated onto theobject to be exposed, of exposure fields of the object to be exposed.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts a scanning cycle of the scanning unit in correspondence with theminimum scanning width of the scanning unit.

In the electron beam exposure apparatus, the adjustment unit adjusts adeflection cycle of the deflector in correspondence with the minimumdeflection width of the deflector.

In the electron beam exposure apparatus, the adjustment unit dynamicallyadjusts the sizes of the intermediate images to be projected onto theobject to be exposed in correspondence with the minimum scanning widthof the scanning unit.

The electron beam exposure apparatus further comprises an illuminationelectron optical system which is inserted between the electron sourceand the plurality of elementary electron optical systems, and is adaptedto convert the electrons emitted by the electron source intosubstantially collimated electron beams, and to irradiate the electronbeams onto the plurality of elementary electron optical systems, andwherein the adjustment unit dynamically adjusts the sizes of theintermediate images to be projected onto the object to be exposed byadjusting a focal length of the illumination electron optical system.

In the electron beam exposure apparatus, the deflector comprises firstand second deflectors, the first deflector scans the intermediate imagesto be projected onto the object to be exposed within an elementaryexposure field so as to expose a subfield made up of a set of elementaryexposure fields, and the second deflector switches the subfield to beexposed every time exposure of the subfield is complete.

In the electron beam exposure apparatus, the first deflector comprisesan electrostatic type deflector, and the second deflector comprises anelectromagnetic type deflector.

According to the another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronsource for emitting electrons, a plurality of elementary electronoptical systems for respectively forming intermediate images of theelectron source, a projection electron optical system for projecting theplurality of intermediate images onto the object to be exposed, and ascanning unit for scanning the plurality of intermediate images to beprojected onto the object to be exposed, comprises the step ofdynamically adjusting a minimum scanning width of the scanning unit incorrespondence with fields to be exposed of a pattern to be drawn byexposure on the object to be exposed.

According to still another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronsource for emitting electrons, a projection electron optical system forprojecting an image of the electron source onto the object to beexposed, and a scanning unit for scanning the image of the electronsource to be projected onto the object to be exposed, comprises the stepof dynamically adjusting a minimum scanning width of the scanning unitin correspondence with fields to be exposed of a pattern to be drawn byexposure on the object to be exposed.

According to still another aspect of the present invention, a method ofgenerating exposure control data used for controlling an electron beamexposure apparatus, which has an electron source for emitting electrons,a plurality of elementary electron optical systems for respectivelyforming intermediate images of the electron source, a projectionelectron optical system for projecting the plurality of intermediateimages onto the object to be exposed, and a scanning unit for scanningthe plurality of intermediate images to be projected onto the object tobe exposed, comprises the steps of dividing a pattern to be drawn byexposure on the object to be exposed into a plurality of blocks,detecting features of patterns in the blocks, determining minimumscanning widths of the scanning unit in units of blocks on the basis ofthe features of the patterns in the blocks, and generating exposurecontrol data on the basis of the determination result.

It is still another object of the present invention to achieve highthroughput by dynamically changing the deflection width of an electronbeam and the moving velocity of a stage upon forming a single pattern byexposure.

An electron beam exposure apparatus according to one aspect of thepresent invention is an electron beam exposure apparatus, which has anelectron beam source for generating a plurality of electron beams, aprojection electron optical system for projecting images formed by theplurality of electron beams onto an object to be exposed, a deflectorfor deflecting the plurality of electron beams, and a stage for movingthe object to be exposed, and which sequentially exposes dividedexposure fields obtained by dividing an exposure pattern in a movingdirection of the stage while continuously moving the object to beexposed by the stage, comprising a deflection width adjustment unit fordynamically adjusting a minimum deflection width of the deflector incorrespondence with the fields to be exposed of the exposure pattern,and a moving velocity adjustment unit for dynamically adjusting movingvelocities of the stage in units of divided exposure fields incorrespondence with exposure times required for exposing the respectivedivided exposure fields while deflecting the plurality of electron beamsby the deflector.

In the electron beam exposure apparatus, the moving velocity adjustmentunit adjusts the moving velocities of the stage in units of dividedexposure fields so as to make the stage move by a length of thecorresponding divided exposure field in the moving direction of thestage within the exposure time of the divided exposure field.

In the electron beam exposure apparatus, each of the divided exposurefields is made up of at least one unit exposure field formed by a matrixof a plurality of elementary exposure fields each of which is exposed byone electron beam, and the deflection width adjustment unit adjusts theminimum deflection width of the deflector in units of unit exposurefields.

In the electron beam exposure apparatus, each of the divided exposurefields is made up of a matrix of a plurality of unit exposure fields indirections perpendicular to the moving direction of the stage.

In the electron beam exposure apparatus, the deflection width adjustmentunit adjusts the minimum deflection width of the deflector in units ofunit exposure fields on the basis of a feature of an exposure pattern inthe corresponding unit exposure region.

In the electron beam exposure apparatus, the deflection width adjustmentunit adjusts the minimum deflection width of the deflector in units ofunit exposure fields on the basis of a minimum line width of an exposurepattern in the corresponding unit exposure region.

The electron beam exposure apparatus further comprises an adjustmentunit for adjusting sizes of the electron beams on the object to beexposed in correspondence with the minimum deflection width of thedeflector.

In the electron beam exposure apparatus, the exposure time for each unitdivided exposure field is determined on the basis of the number of timesof settlement, a settling wait time, and a settling time of the electronbeam in the corresponding divided exposure field.

In the electron beam exposure apparatus, the moving velocity adjustmentunit adjusts the moving velocities of the stages in units of dividedexposure fields to fall within a range in which a difference between themoving velocity of the stage upon exposing one divided exposure field,and the moving velocity of the stage upon exposing the neighboringdivided exposure field of the one divided exposure field becomes notmore than a predetermined value.

According to another aspect of the present invention, an electron beamexposure apparatus, which has an electron beam source for generating aplurality of electron beams, a projection electron optical system forprojecting images formed by the plurality of electron beams onto anobject to be exposed, a deflector for deflecting the plurality ofelectron beams, and a stage for moving the object to be exposed, andwhich sequentially exposes frames obtained by dividing an exposurepattern along a moving direction of the stage while continuously movingthe object to be exposed by the stage, comprises a deflection widthadjustment unit for dynamically adjusting a minimum deflection width ofthe deflector in correspondence with fields to be exposed of theexposure pattern, and a moving velocity adjustment unit for adjustingmoving velocities of the stage in units of frames.

According to still another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronbeam source for generating a plurality of electron beams, a projectionelectron optical system for projecting images formed by the plurality ofelectron beams onto an object to be exposed, a deflector for deflectingthe plurality of electron beams, and a stage for moving the object to beexposed, and which sequentially exposes divided exposure fields obtainedby dividing an exposure pattern in a moving direction of the stage whilecontinuously moving the object to be exposed by the stage, comprises thedeflection width adjustment step of dynamically adjusting a minimumdeflection width of the deflector in correspondence with the fields tobe exposed of the exposure pattern, and the moving velocity adjustmentstep of dynamically adjusting moving velocities of the stage in units ofdivided exposure fields in correspondence with exposure times requiredfor exposing the respective divided exposure fields while deflecting theplurality of electron beams by the deflector.

According to still another aspect of the present invention, a method ofcontrolling an electron beam exposure apparatus, which has an electronbeam source for generating a plurality of electron beams, a projectionelectron optical system for projecting images formed by the plurality ofelectron beams onto an object to be exposed, a deflector for deflectingthe plurality of electron beams, and a stage for moving the object to beexposed, and which sequentially exposes frames obtained by dividing anexposure pattern along a moving direction of the stage whilecontinuously moving the object to be exposed by the stage, comprises thedeflection width adjustment step of dynamically adjusting a minimumdeflection width of the deflector in correspondence with fields to beexposed of the exposure pattern, and the moving velocity adjustment stepof adjusting moving velocities of the stage in units of frames.

According to still another aspect of the present invention, a method ofgenerating exposure control data used for controlling an electron beamexposure apparatus, which has an electron beam source for generating aplurality of electron beams, a projection electron optical system forprojecting images formed by the plurality of electron beams onto anobject to be exposed, a deflector for deflecting the plurality ofelectron beams, and a stage for moving the object to be exposed, andwhich sequentially exposes divided exposure fields obtained by dividingan exposure pattern in a moving direction of the stage whilecontinuously moving the object to be exposed by the stage, comprises thesteps of dividing the exposure pattern into a plurality of blocks,detecting features of exposure patterns in the blocks, determiningminimum deflection widths of the deflector in units of blocks on thebasis of the features of the exposure patterns in the blocks,calculating exposure times required for exposing individual dividedexposure fields, each of which includes at least one block, whiledeflecting the plurality of electron beams by the deflector, on thebasis of the minimum deflection widths and shapes of the exposurepatterns pertaining to the respective blocks, determining movingvelocities of the stages in units of divided exposure fields inaccordance with the calculated exposure times of the individual dividedexposure fields, and generating exposure control data on the basis ofthe determined minimum deflection widths and moving velocities.

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description of embodimentsof the present invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a principal part of an electron beamexposure apparatus according to the present invention;

FIG. 2 is a view for explaining an elementary electron optical systemarray 3;

FIG. 3 is a view for explaining an elementary electron optical system;

FIGS. 4A and 4B are views for explaining the electrodes of theelementary electron optical system;

FIG. 5 is a block diagram for explaining the system arrangementaccording to the present invention;

FIGS. 6A and 6B are views. for explaining an elementary exposure field(EF) and an subarray exposure field (SEF);

FIGS. 7A and 7B are views for explaining the subfields;

FIG. 8 is a view for explaining the relationship between the subfieldsand the pattern area;

FIG. 9 is a flow chart for explaining generation of exposure controldata;

FIGS. 10A to 10C are views for explaining the process of determining theexposure patterns to be drawn by the respective elementary electronoptical systems and the matrix regions defined by a deflector;

FIG. 11 is a view for explaining exposure control data;

FIG. 12 is a flow chart for explaining exposure based on the exposurecontrol data;

FIG. 13 is a flow chart for explaining the manufacturing flow ofmicrodevices;

FIG. 14 is a flow chart for explaining the wafer process;

FIGS. 15A to 15D a re view s for explaining a conventionalmulti-electron beam type exposure apparatus;

FIG. 16 is a flow chart for explaining generation of exposure controldata;

FIG. 17 is a view for explaining the exposure control data;

FIG. 18 is a flow chart for explaining exposure based on the exposurecontrol data;

FIG. 19 is a schematic view showing a principal part of an electron beamexposure apparatus according to the present invention;

FIG. 20 is a block diagram for explaining the system arrangementaccording to the present invention;

FIG. 21 is a view for explaining elementary exposure fields (EF),subfields (SF), and main fields (MF);

FIG. 22 is a flow chart for explaining generation of exposure controldata;

FIGS. 23A to 23C are graphs for explaining the relationship between theexposure time and stage moving velocity in units of main fields;

FIG. 24 is a view for explaining the exposure control data;

FIG. 25 is a flow chart for explaining exposure based on the exposurecontrol data;

FIG. 26 is a flow chart for explaining the method of re-determining thestage moving velocity in units of main fields; and

FIG. 27 is a view for explaining a matrix of frames.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[First Embodiment]

(Explanation of Constituting Elements of Electron Beam ExposureApparatus)

FIG. 1 is a schematic view showing a principal part of an electron beamexposure apparatus according to the present invention.

Referring to FIG. 1, reference numeral 1 denotes an electron gun made upof a cathode 1 a, grid 1 b, and anode 1 c. Electrons emitted by thecathode 1 a form a crossover image between the grid 1 b and anode 1 c.The crossover image will be referred to as an electron sourcehereinafter.

Electrons coming from this electron source are converted into nearlycollimated electron beams by an illumination electron optical system 2whose front-side focal point position is located at the electron sourceposition. The nearly collimated electron beams illuminate an elementaryoptical system array 3. The illumination electron optical system 2 ismade up of electron lenses 2 a, 2 b, and 2 c. By adjusting the electronoptical powers (focal lengths) of at least two of the electron lenses 2a, 2 b, and 2 c, the focal length of the illumination electron opticalsystem 2 can be changed while holding its focal point position on theelectron source side. In other words, the focal length of theillumination electron optical system 2 can be changed while obtainingnearly collimated electron beams from the illumination electron opticalsystem 2.

The nearly collimated electron beams coming from the illuminationelectron optical system 2 enter the elementary electron optical systemarray 3. The elementary electron optical system array 3 is formed byarranging a plurality of elementary electron optical systems, eachconsisting of an aperture, electron lens, and blanking electrode, indirections perpendicular to an optical axis AX. The elementary electronoptical system 3 will be explained in detail later.

The elementary electron optical system array 3 forms a plurality ofintermediate images of the electron source. These intermediate imagesare projected in a reduced scale by a reduction electron optical system4 (to be described later), and form images of the electron source on awafer 5. Note that the size Wm of the intermediate image of the electronsource is given by:

Wm=Ws×Fe/Fi

where Ws is the size of the electron source, Fi is the focal length ofthe illumination electron optical system 2, and Fe is the focal lengthof each electron optical system of the elementary electron opticalsystem.

Hence, when the focal length of the illumination electron optical system2 is changed, the sizes of the plurality of intermediate images of theelectron source can be changed at the same time. Therefore, the sizes ofa plurality of electron source images on the wafer 5 can be changed atthe same time. Upon changing the focal length of the illuminationelectron optical system 2, the optical axis of the illumination electronoptical system 2 may change accordingly. More specifically, thepositional relationship between the illumination electron optical system2 and electron source changes before and after the focal length of theillumination electron optical system 2 is changed. As a consequence, thepositions of the intermediate images of the electron source deviatebefore and after the focal length of the illumination electron opticalsystem 2 is changed, and the plurality of electron source images on thewafer 5 undergo position deviations before and after the focal length ofthe illumination electron optical system 2 is changed. Reference symbolAD denotes an axis adjustment deflector for moving the position of theelectron source relative to the illumination electron optical system 2in the X- and Y-directions. By adjusting the position of the electronsource relative to the illumination electron optical system 2, theposition deviations of the intermediate images of the electron sourcebefore and after the change in focal length of the illumination electronoptical system 2 are corrected, thereby correcting the positiondeviations of the plurality of electron images on the wafer 5.

The focal lengths of elementary electron optical systems are set to beapproximately equal to each other to obtain nearly equal sizes of theelectron source images on the wafer 5. Furthermore, the elementaryelectron optical system array 3 makes the positions of the individualintermediate images differ in the optical axis direction incorrespondence with the curvature of field of the reduction electronoptical system 4, and corrects in advance any aberrations expected to beproduced when the individual intermediate images are projected onto thewafer 5 in a reduced scale by the reduction electron optical system 4.

The reduction electron optical system 4 comprises a symmetric magneticdoublet consisting of a first projection lens 41 (43) and secondprojection lens 42 (44). If f1 represents the focal length of the firstprojection lens 41 (43), and f2 represents the focal length of thesecond projection lens 42 (44), the distance between these two lenses isf1+f2. The object point on the optical axis AX is located at the focalpoint position of the first projection lens 41 (43), and its image pointis formed at the focal point of the second projection lens 42 (44). Thisimage is reduced to −f2/f1. Since two lens magnetic fields aredetermined to act in opposite directions, the Seidel aberrations andchromatic aberrations pertaining to rotation and magnificationtheoretically cancel each other, except for five aberrations, i.e.,spherical aberration, isotropic astigmatism, isotropic coma, curvatureof field, and on-axis chromatic aberration.

Reference numeral 6 denotes a deflector for deflecting a plurality ofelectron beams coming from the elementary electron optical system array3 to displace a plurality of electron source images by nearly equaldeflection amounts in the X- and Y-directions on the wafer 5. Thedeflector 6 comprises a main deflector 61 which has a large deflectionwidth but requires a long time until settlement, i.e., a long settlementwait time, and a sub deflector 62 which has a small deflection width butrequires only a short settlement wait time. The main deflector 61 is anelectromagnetic type deflector, and the sub deflector 62 is anelectrostatic type deflector.

Reference numeral 7 denotes a dynamic focus coil that corrects anydeviations of the focus positions of the electron source images arisingfrom deflection aberration produced upon operation of the deflector 6;and 8, a dynamic stigmatic coil that corrects astigmatism of deflectionaberration produced upon deflection as in the dynamic focus coil 7.

Reference numeral 9 denotes a reflected electron detector for detectingreflected or secondary electrons produced when electron beams comingfrom the elementary electron optical system array 3 strike alignmentmarks formed on the wafer 5 or marks on a stage reference plate 13.

Reference numeral 10 denotes a Faraday cup having two single knife edgesrespectively extending in the X- and Y-directions. The Faraday cupdetects the charge amount of electron source images formed by theelectron beams coming from the elementary electron optical systems.

Reference numeral 11 denotes a θ-Z stage that carries a wafer, and ismovable in the direction of the optical axis AX (Z-axis) and in thedirection of rotation about the Z-axis. The above-mentioned stagereference plate 13 and the Faraday cup 10 are fixed on the stage 11.

Reference numeral 12 denotes an X-Y stage which carries the θ-Z stageand is movable in the X- and Y-directions perpendicular to the directionof the optical axis AX (Z-axis).

In the elementary electron optical system array 3, a plurality ofelementary electron optical systems form a group (subarray), and aplurality of subarrays are formed. In the example shown in FIG. 2, fivesubarrays A to E are formed. In each subarray, a plurality of elementaryelectron optical systems are two-dimensionally arranged, and 27elementary electron optical systems (e.g., C(1,1) to C(3,9)) are formedin each subarray.

FIG. 3 is a sectional view of each elementary electron optical system.

Referring to FIG. 3, a substrate AP-P is irradiated with electron beamsnearly collimated by the illumination electron optical system 2. Thesubstrate AP-P has an aperture (AP1) that defines the shape of electronbeams to be transmitted, and is common to other elementary electronoptical systems. That is, the substrate AP-P is a substrate having aplurality of apertures.

Reference numeral 301 denotes a blanking electrode which is made up of apair of electrodes and has a deflection function; and 302, a substratewhich has an aperture (AP2) larger than the aperture (AP1) and is commonto other elementary electron optical systems. On the substrate 302, theblanking electrode 301 and wiring (W) for turning on/off the electrodesare formed. That is, the substrate 302 has a plurality of apertures anda plurality of blanking electrodes.

Reference numeral 303 denotes an electron optical system, which uses twounipotential lenses 303 a and 303 b. Each unipotential lens is made upof three aperture electrodes, and has a convergence function by settingthe upper and lower electrodes at the same potential as an accelerationpotential V0, and keeping the intermediate electrode at anotherpotential V1 or V2. The individual aperture electrodes are stacked on asubstrate via insulating materials, and the substrate is common to otherelementary electron optical systems. That is, the substrate has aplurality of electron optical systems 303.

The upper, intermediate, and lower electrodes of the unipotential lens303 a and the upper and lower electrodes of the unipotential lens 303 bhave a shape shown in FIG. 4A, and the upper and lower electrodes of theunipotential lenses 303 a and 303 b are set at a common potential in allthe elementary electron optical systems by a first focal pointastigmatism control circuit 15 (to be described later).

Since the potential of the intermediate electrode of the unipotentiallens 303 a can be set by the first focal point astigmatism controlcircuit 15 in units of elementary electron optical systems, the focallength of the unipotential lens 303 a can be set in units of elementaryelectron optical systems.

The intermediate electrode of the unipotential lens 303 b is made up offour electrodes, as shown in FIG. 4B, and the potentials of theseelectrodes can be set independently and also individually in units ofelementary electron optical systems by the first focal point astigmatismcontrol circuit 15. Hence, the unipotential lens 303 b can havedifferent focal lengths in a section perpendicular to its optical axisand can set them individually in units of elementary electron opticalsystems.

As a consequence, by respectively controlling the potentials of theintermediate electrodes of the electron optical systems 303, theelectron optical characteristics (the intermediate image formingpositions and astigmatism) of the elementary electron optical systemscan be controlled. Upon controlling the intermediate image formingpositions, since the size of each intermediate image is determined bythe ratio between the focal lengths of the illumination electron opticalsystem 2 and each electron optical system 303, the intermediate imageforming position is moved by setting a constant focal length of eachelectron optical system 303 and moving its principal point position.With this control, the intermediate images formed by all the elementaryelectron optical systems can have nearly equal sizes and differentpositions in the optical axis direction.

Each nearly collimated electron beam output from the illuminationelectron optical system 2 forms an intermediate image of the electronsource via the aperture (AP1) and electron optical system 303. Note thatthe aperture (AP1) is located at or in the vicinity of the front-sidefocal point position of the corresponding electron optical system 303,and the blanking electrode 301 is located at or in the vicinity of theintermediate image forming position (rear-side focal point position) ofthe corresponding electron optical system 303. For this reason, if noelectric field is applied across the electrodes of the blankingelectrode 301, the electron beam is not deflected, as indicated by anelectron beam 305 in FIG. 3. On the other hand, if an electric field isapplied across the electrodes of the blanking electrode 301, theelectron beam is deflected, as indicated by an electron beam 306 in FIG.3. Since the electron beams 305 and 306 have different angledistributions on the object plane of the reduction electron opticalsystem 4, they become incident on different regions at the pupilposition (on a plane P in FIG. 1) of the reduction electron opticalsystem 4. Hence, a blanking aperture BA that transmits the electron beam305 alone is formed at the pupil position (on the plane P in FIG. 1) ofthe reduction electron optical system.

The electron optical systems 303 of the elementary electron opticalsystems individually set the potentials of their two intermediateelectrodes so as to correct the curvature of field and astigmatismproduced when the intermediate images formed thereby are projected in areduced scale onto the surface to be exposed by the reduction electronoptical system 4, thereby making the electron optical characteristics(intermediate image forming positions and astigmatism) of the elementaryelectron optical systems different. However, in this embodiment, inorder to decrease the number of wiring lines between the intermediateelectrodes and the first focal point-astigmatism control circuit 15, theelementary electron optical systems included in a single subarray haveidentical electron optical characteristics, and the electron opticalcharacteristics (intermediate image forming positions and astigmatism)of the elementary electron optical systems are controlled in units ofsubarrays.

Furthermore, in order to correct distortion produced when a plurality ofintermediate images are projected in a reduced scale onto the surface tobe exposed by the reduction electron optical system 4, the distortioncharacteristics of the reduction electron optical system 4 are detectedin advance, and the positions of the elementary electron optical systemsin directions perpendicular to the optical axis of the reductionelectron optical system 4 are set based on the detected characteristics.

FIG. 5 shows the system arrangement of this embodiment. An axis controlcircuit AXC controls the axis adjustment deflector AD to correct theposition deviations of the intermediate images of the electron sourcebefore and after the change in focal length of the illumination electronoptical system 2. A focal length control circuit FC controls the focallength of the illumination electron optical system 2 while holding itsfocal point position on the electron source side, by adjusting theelectron optical powers (focal lengths) of at least two of the electronlenses 2 a, 2 b, and 2 c.

A blanking control circuit 14 individually ON/OFF-controls the blankingelectrodes of the elementary electron optical systems in the elementaryelectron optical system array 3, and the first focal point-astigmatismcontrol circuit 15 individually controls the electron opticalcharacteristics (intermediate image forming positions and astigmatism)of the elementary electron optical systems in the elementary electronoptical system array 3.

A second focal point-astigmatism control circuit 16 controls the focalpoint position and astigmatism of the reduction electron optical system4 by controlling the dynamic stigmatic coil 8 and dynamic focus coil 7.A deflection control circuit 17 controls the deflector 6. Amagnification adjustment circuit 18 adjusts the magnification of thereduction electron optical system 4. An optical characteristicadjustment circuit 19 adjusts rotation aberration and optical axisposition by changing the excitation currents of electromagnetic lensesthat make up the reduction electron optical system 4.

A stage drive control circuit 20 controls driving of the θ-Z stage, andalso controls driving of the X-Y stage 12 in collaboration with a laserinterferometer 21 that detects the position of the X-Y stage 12.

A control system 22 synchronously controls the above-mentioned controlcircuits, reflected electron detector 9, and Faraday cup 10 to attainexposure and alignment based on exposure control data from a memory 23.The control system 22 is controlled by a CPU 25 for controlling theentire electron beam exposure apparatus via an interface 24.

(Explanation of Operation)

Exposure operation by the electron beam exposure apparatus of thisembodiment will be explained below with the aid of FIG. 5.

The control system 22 directs the deflection control circuit 17 based onthe exposure control data from the memory 23 to deflect a plurality ofelectron beams from the elementary electron optical system array by thesub deflector 62 of the deflector 6. Also, the control system 22 directsthe blanking control circuit 14 to turn on/off the blanking electrodesof the respective elementary electron optical systems in accordance withthe pattern to be formed by exposure on the wafer 5. At this time, theX-Y stage 12 is continuously moving in the X-direction. An electron beamcoming from one elementary electron optical system scans and exposes anexposure field (EF) on the wafer 5 to have the full square as a startpoint, as shown in FIG. 6A. Also, as shown in FIG. 6B, the exposurefields (EF) of the plurality of elementary electron optical systems ineach subarray are set adjacent to each other. Consequently, a subarrayexposure field (SEF) including a plurality of exposure fields (EF) isexposed on the wafer 5. At the same time, a subfield made up of subarrayexposure fields (SEF) respectively formed by the subarrays A to E isexposed on the wafer 5, as shown in FIG. 7A. In other words, thesubfield made up of a plurality of elementary exposure fields (EF) isexposed.

The control system 22 directs the deflection control circuit 17 todeflect a plurality of electron beams coming from the elementaryelectron optical system array using the main deflector 61 of thedeflector 6 so as to expose subfield 2 after exposure of subfield 1shown in FIG. 7B. Again, as described above, the control system 22directs the deflection control circuit 17 to deflect a plurality ofelectron beams coming from the elementary electron optical system arrayby the sub deflector 62 of the deflector 6, and directs the blankingcontrol circuit 14 to turn on/off the blanking electrodes of therespective elementary electron optical systems in accordance with thepattern to be formed by exposure on the wafer 5, thus exposing subfield2. The subfields are then exposed in turn like subfields 3 and 4, asshown in FIG. 7B, thus forming the pattern on the wafer 5. Morespecifically, as shown in FIG. 8, if PA represents a pattern area basedon pattern data, the electron beam exposure apparatus of this embodimentsequentially exposes the pattern area PA in units of subfields.

Some methods pertaining to generation of the exposure control data andthe exposure procedure based on the exposure control data will beexemplified below.

<First Method>

(Explanation of Generation of Exposure Control Data)

The method of generating exposure control data of the electron beamexposure apparatus of this embodiment will be explained below.

Upon reception of pattern data to be formed by exposure on the wafer,the CPU 25 executes processing for generating exposure control data, asshown in FIG. 9.

The respective steps will be described.

(Step S101)

The input pattern data is segmented into data in units of subfieldsdefined by the electron beam exposure apparatus of this embodiment.

(Step S102)

One subfield is selected.

(Step S103)

A deflection position (reference position) defined by the main deflector61 upon exposing the selected subfield is determined.

(Step S104)

Feature information (e.g., the minimum line width, type of line width,shape) of a pattern is detected from the pattern data of the selectedsubfield. In this embodiment, the minimum line width is detected.

(Step S105)

The minimum deflection width that the sub deflector 62 gives to anelectron beam is determined based on the detected feature information.In this embodiment, the minimum deflection width is determined so thatan integer multiple of the minimum deflection width agrees with thematrix pitch (on the wafer) of a plurality of electron beams andapproximately ¼ the minimum line width.

(Step S106)

An electron beam diameter optimal for the determined minimum deflectionwidth (the size of an electron beam imaged on the wafer) is determined.In this embodiment, the electron beam diameter is determined to benearly equal to the diameter of a circumscribed circle of a squarehaving one side equal to the minimum deflection width.

(Step S107)

The pattern data of the selected subfield is segmented into pattern datain units of elementary exposure fields corresponding to the elementaryelectron optical systems, and a common matrix made up of matrix elementsFME using the determined minimum deflection amount of the sub deflector62 as a matrix spacing is set, thus converting the pattern data intothose expressed on the common matrix in units of elementary electronoptical systems. The processing pertaining to pattern data upon exposureusing two elementary electron optical systems a and b will be describedbelow for the sake of simplicity.

FIGS. 10A and 10B show patterns Pa and Pb to be formed by exposure bythe neighboring elementary electron optical systems a and b on a commondeflection matrix DM. Each elementary electron optical system irradiatesan electron beam onto the wafer by turning off its blanking electrode athatched matrix positions with pattern portions. For this purpose, theCPU 25 determines first regions FF (solid black portions) consisting ofmatrix positions corresponding to exposure positions of at least one ofthe elementary electron optical systems a and b, and second regions NN(blank portions) consisting of matrix positions when neither of theelementary electron optical systems a and b commonly performs exposure,as shown in FIG. 10C, on the basis of the matrix position data to beexposed in units of elementary electron optical systems shown in FIGS.10A and 10B. When a plurality of electron beams are located on the firstregion FF on the matrix, exposure is done by deflecting and settling theelectron beams by the deflector 6 in units of minimum deflection amounts(the matrix spacings), thus forming all the patterns to be drawn on thewafer by exposure. When a plurality of electron beams are located on thesecond region NN on the matrix, they are deflected without settlingtheir positions, thereby attaining exposure while eliminatingunnecessary deflection of the electron beams. In other words, afterexposure of the first region (FF), when the electron beams are deflectedto expose the next first region (FF) while skipping the second region(NN), the number of times of deflection that requires a long settlingtime can be reduced, and exposure can be attained within a shorterperiod of time. Subsequently, the CPU 25 determines the matrix positionsof matrix elements to be exposed on the basis of data pertaining to theregions FF and NN shown in FIG. 10C. Also, the CPU 25 determines theON/OFF patterns of blanking electrodes corresponding to the matrixpositions to be settled of the electron beams in units of elementaryelectron optical systems on the basis of data representing the patternsshown in FIGS. 10A and 10B. Since matrix numbers are assigned in advanceto the respective matrix elements, the matrix numbers are determined asthe matrix positions.

(Step S108)

It is checked if the processing in steps S103 to S107 is complete forall the subfields. If non-processed subfields remain, the flow returnsto step S102 to select the non-processed subfield.

(Step S109)

Upon completion of the processing in steps S103 to S107 for all thesubfields, exposure control data is stored. As shown in FIG. 11, theexposure control data contains as elements the reference positions andelectron beam diameters defined by the main deflector 61, the minimumdeflection width of the sub deflector 62, the matrix positions definedby the sub deflector 62, and the ON/OFF states of the electron beamirradiation of the respective elementary electron optical systems at thecorresponding matrix positions.

In this embodiment, the above-mentioned processing steps are implementedby the CPU 25 of the electron beam exposure apparatus but may beimplemented by another processing device, and the obtained exposurecontrol data may be transferred to the CPU 25 to achieve the aboveobject and to obtain the same effects as above.

(Explanation of Exposure Based on Exposure Control Data)

When the CPU 25 instructs the control system 22 to “execute exposure”via the interface 24, the control system 22 executes the steps shown inFIG. 12 on the basis of the exposure control data on the memory 23 inresponse to this instruction.

The individual steps will be explained below.

(Step S201)

The control system directs the focal length control circuit Fc to adjustthe electron optical powers (focal lengths) of at least two of theelectron lenses 2 a, 2 b, and 2 c that make up the illumination electronoptical system 2, so as to obtain the electron beam diameterscorresponding to the subfield to be exposed. In this way, the focallength of the illumination electron optical system 2 is adjusted whileholding the focal point position of the illumination electron opticalsystem 2 on the electron source side, thereby changing the sizes(electron beam diameters) of a plurality of electron source images onthe wafer 5 to that designated by the exposure control data.

(Step S202)

In order to correct the position deviations of the electron sourceimages before and after the change in focal length of the illuminationelectron optical system 2, the control system 22 directs the axiscontrol circuit AXC to move the position of the electron source relativeto the illumination electron optical system 2 in the X- and Y-directionsby the axis adjustment deflector AD, thereby correcting the positiondeviations.

(Step S203)

The control system 22 directs the deflection control circuit 17 todeflect a plurality of electron beams coming from the elementaryelectron optical system array by the main deflector 61 so that theelectron beams are located at the reference positions upon exposing thesubfield. Furthermore, the control system 22 directs the second focalpoint astigmatism control circuit 16 to control the dynamic focus coil 7in correspondence with the deflection attained by the main deflector 61on the basis of dynamic focal point correction data obtained in advanceto correct the focal point position of the reduction electron opticalsystem 4, and to control the dynamic stigmatic coil 8 on the basis ofdynamic astigmatism correction data obtained in advance to correctastigmatism of the reduction electron optical system.

(Step S204)

The control system 22 directs the deflection control circuit 17 toswitch the minimum deflection width of the sub deflector 62 to thatcorresponding to the subfield to be exposed, and to deflect a pluralityof electron beams coming from the elementary electron optical systemarray in units of switched minimum deflection widths by the subdeflector 62. Also, the control system 22 directs the blanking controlcircuit 14 to turn on/off the blanking electrodes of the elementaryelectron optical systems in correspondence with the pattern to be formedby exposure on the wafer 5. At this time, the X-Y stage 12 iscontinuously moving in the X-direction, and the deflection controlcircuit 17 controls the deflection positions of the electron beams inconsideration of the moving amount of the X-Y stage 12. As a result, anelectron beam coming from one elementary electron optical system scansand exposes an exposure field (EF) on the wafer 5 to have a full squareas a start point, as shown in FIG. 6A. Also, as shown in FIG. 6B, theexposure fields (EF) of the plurality of elementary electron opticalsystems in each subarray are set adjacent to each other. Consequently, asubarray exposure field (SEF) including a plurality of exposure fields(EF) is exposed on the wafer 5. At the same time, a subfield made up ofsubarray exposure fields (SEF) respectively formed by the subarrays A toE is exposed on the wafer 5, as shown in FIG. 7A. In other words, thesubfield made up of a plurality of elementary exposure fields (EF) isexposed.

(Step S205)

If the next subfield to be exposed remains, the flow returns to stepS201; otherwise, exposure ends.

<Second Method>

(Explanation of Generation of Exposure Control Data)

The method of generating exposure control data of the electron beamexposure apparatus of this embodiment will be explained below.

Upon reception of pattern data to be formed by exposure on the wafer,the CPU 25 executes processing for generating exposure control data, asshown in FIG. 16.

The respective steps will be described.

(Step S301)

The input pattern data is segmented into data in units of subfieldsdefined by the electron beam exposure apparatus of this embodiment.

(Step S302)

One subfield is selected.

(Step S303)

A deflection position (reference position) defined by the main deflector61 upon exposing the selected subfield is determined.

(Step S304)

Feature information (e.g., the minimum line width, type of line width,shape) of a pattern is detected from the pattern data of the selectedsubfield. In this embodiment, the minimum line width is detected.

(Step S305)

The minimum deflection width that the sub deflector 62 gives an electronbeam is determined based on the detected feature information. In thisembodiment, the minimum deflection width is determined so that aninteger multiple of the minimum deflection width agrees with the matrixpitch (on the wafer) of a plurality of electron beams and approximately¼ the minimum line width.

(Step S306)

The size of a dot pattern that each electron beam forms on a resist onthe wafer must be changed in correspondence with the determined minimumdeflection width. In this embodiment, the electron beam diameter (thesize of the electron beam to be imaged on the wafer) is fixed, and thetime for which the electron beam undergoes settlement at the deflectionposition (so-called exposure time) is changed, thereby changing the sizeof the dot pattern. More specifically, when the minimum deflection widthis increased, the settling time is prolonged to increase the size of thedot pattern. Normally, if Ts represents the settling time of theelectron beam at the deflection position, and To represents the settlingwait time until the electron beam is deflected and-settles to a desireddeflection position, a deflection cycle Td of the sub deflector 62 isgiven by Td=Ts+To. For this reason, in this embodiment, since To isnearly constant, the deflection cycle Td of the sub deflector 62 ischanged in correspondence with the determined minimum deflection width,thereby changing the size of a dot pattern. Hence, the deflection cycleTd of the sub deflector 62 is determined based on the determined minimumdeflection width, the current density of the electron beam, the electronbeam diameter, and the resist sensitivity. At this time, the size of thedot pattern is set to be nearly equal to a circumscribed circle of asquare having one side equal to the minimum deflection width.

(Step S307)

The pattern data of the selected subfield is segmented into pattern datain units of elementary exposure fields corresponding to the elementaryelectron optical systems, and a common matrix made up of matrix elementsFME using the determined minimum deflection amount of the sub deflector62 as a matrix spacing is set, thus converting the pattern data intothose expressed on the common matrix in units of elementary electronoptical systems. The processing pertaining to pattern data upon exposureusing two elementary electron optical systems a and b will be describedbelow for the sake of simplicity.

FIGS. 10A and 10B show patterns Pa and Pb to be formed by exposure bythe neighboring elementary electron optical systems a and b on a commondeflection matrix DM. More specifically, each elementary electronoptical system irradiates an electron beam onto the wafer by turning offits blanking electrode at hatched matrix positions with patternportions. For this purpose, the CPU 25 determines first regions FF(solid black portions) consisting of matrix positions corresponding toexposure positions of at least one of the elementary electron opticalsystems a and b, and second regions NN (blank portions) consisting ofmatrix positions when neither of the elementary electron optical systemsa and b commonly performs exposure, as shown a in FIG. 10C, on the basisof the matrix position data to be exposed in units of elementaryelectron optical systems shown in FIGS. 10A and 10B. When a plurality ofelectron beams are located on the first region FF on the matrix,exposure is done by deflecting and settling the electron beams by thedeflector 6 in units of minimum deflection amounts (the matrixspacings), thus forming all the patterns to be drawn on the wafer byexposure. When a plurality of electron beams are located on the secondregion NN on the matrix, they are deflected without settling theirpositions, thereby attaining exposure while eliminating unnecessarydeflection of the electron beams. In other words, after exposure of thefirst region (FF), when the electron beams are deflected to expose thenext first region (FF) while skipping the second region (NN), the numberof times of deflection that requires a long settling time can bereduced, and exposure can be attained within a shorter period of time.Subsequently, the CPU 25 determines the matrix positions of matrixelements to be exposed on the basis of data pertaining to the regions FFand NN shown in FIG. 10C. Also, the CPU 25 determines the ON/OFFpatterns of blanking electrodes corresponding to the matrix positions tobe settled of the electron beams in units of elementary electron opticalsystems on the basis of data representing the patterns shown in FIGS.10A and 10B. Since matrix numbers are assigned in advance to therespective matrix elements, the matrix numbers are determined as thematrix positions.

(Step S308)

It is checked if the processing in steps S303 to S307 is complete forall the subfields. If non-processed subfields remain, the flow returnsto step S302 to select the non-processed subfield.

(Step S309)

Upon completion of the processing in steps S303 to S307 for all thesubfields, exposure control data is stored. As shown in FIG. 17, theexposure control data contains as elements the reference positions andelectron beam-diameters defined by the main deflector 61, the minimumdeflection width and deflection cycle of the sub deflector 62, thematrix positions defined by the sub deflector 62, and the ON/OFF statesof the electron beam irradiation of the respective elementary electronoptical systems at the corresponding matrix positions.

In this embodiment, the above-mentioned processing steps are implementedby the CPU 25 of the electron beam exposure apparatus but may beimplemented by another processing device, and the obtained exposurecontrol data may be transferred to the CPU 25 to achieve the aboveobjective and to obtain the same effects as above.

(Explanation of Exposure Based on Exposure Control Data)

When the CPU 25 instructs the control system 22 to “execute exposure”via the interface 24, the control system 22 executes the steps shown inFIG. 18 on the basis of the exposure control data on the memory 23 inresponse to this instruction.

The individual steps will be explained below.

(Step S401)

The control system 22 directs the deflection control circuit 17 to setthe deflection amount of the main deflector 61, so that a plurality ofelectron beams coming from the elementary electron optical system arrayare located at the reference positions upon exposing the subfield.Furthermore, the control system 22 directs the second focal pointastigmatism control circuit 16 to control the dynamic focus coil 7 incorrespondence with the deflection position of the main deflector on thebasis of dynamic focal point correction data obtained in advance tocorrect the focal point position of the reduction electron opticalsystem 4, and to control the dynamic stigmatic coil 8 on the basis ofdynamic astigmatism correction data obtained in advance to correctastigmatism of the reduction electron optical system.

(Step S402)

The control system 22 directs the deflection control circuit 17 toswitch the minimum deflection width and deflection cycle of the subdeflector 62 to those corresponding to the subfield to be exposed.Furthermore, a cycle signal defined by the deflection cycle isgenerated. In synchronism with the cycle signal, a plurality of electronbeams coming from the elementary electron optical system array aredeflected to the deflection positions defined by the exposure controldata by the sub deflector 61 in units of switched minimum deflectionwidths. At the same time, the control system 22 directs the blankingcontrol circuit 14 in synchronism with the cycle signal to turn on/offthe blanking electrodes of the elementary electron optical systems incorrespondence with the pattern to be formed by exposure on the wafer 5.At this time, the X-Y stage 12 is continuously moving in theX-direction, and the deflection control circuit 17 controls thedeflection positions of the electron beams in consideration of themoving amount of the X-Y stage 12. As a result, an electron beam comingfrom one elementary electron optical system scans and exposes anexposure field (EF) on the wafer 5 to have a full square as a startpoint, as shown in FIG. 6A. Also, as shown in FIG. 6B, the exposurefields (EF) of the plurality of elementary electron optical systems ineach subarray are set adjacent to each other. Consequently, a subarrayexposure field (SEF) including a plurality of exposure fields (EF) isexposed on the wafer 5. At the same time, a subfield made up of subarrayexposure fields (SEF) respectively formed by the subarrays A to E isexposed on the wafer 5, as shown in FIG. 7A.

(Step S403)

If the next subfield to be exposed remains, the flow returns to stepS401; otherwise, exposure ends. [Second Embodiment]

(Explanation of Constituting Elements of Electron Beam ExposureApparatus)

FIG. 19 is a schematic view showing a principal part of an electron beamexposure apparatus according to the present invention.

Referring to FIG. 19, reference numeral 1 denotes an electron gun madeup of a cathode 1 a, grid 1 b, and anode 1 c. Electrons emitted by thecathode 1 a form a crossover image between the grid 1 b and anode 1 c.The crossover image will be referred to as an electron sourcehereinafter.

Electrons coming from this electron source are converted into nearlycollimated electron beams by an illumination electron optical system 2whose front-side focal point position is located at the electron sourceposition. The nearly collimated electron beams are irradiated onto anelementary optical system array 3. The illumination electron opticalsystem 2 is made up of electron lenses 2 a, 2 b, and 2 c. By adjustingthe electron optical powers (focal lengths) of at least two of theelectron lenses 2 a, 2 b, and 2 c, the focal length of the illuminationelectron optical system 2 can be changed while holding its focal pointposition on the electron source side. In other words, the focal lengthof the illumination electron optical system 2 can be changed whileobtaining nearly collimated electron beams from the illuminationelectron optical system 2.

The nearly collimated electron beams coming from the illuminationelectron optical system 2 enter an elementary electron optical systemarray 3. The elementary electron optical system array 3 is formed bytwo-dimensionally arranging a plurality of elementary electron opticalsystems, each consisting of an aperture, electron lens, and blankingelectrode, in directions perpendicular to an optical axis AX. Theelementary electron optical system 3 has an arrangement as shown in FIG.2. However, in this embodiment, the matrix of elementary electronoptical systems is different from that in FIG. 2, as will be describedlater.

The elementary electron optical system array 3 is made up of a matrix ofa plurality of elementary electron optical systems shown in FIGS. 3 and4, and these elementary electron optical systems form a plurality ofintermediate images of the electron source. The intermediate images areprojected in a reduced scale by a reduction electron optical system 4,and form images of the electron source on a wafer 5. Note that the sizeWm of the intermediate image of the electron source is given by:

Wm=Ws×Fe/Fi

where Ws is the size of the electron source, Fi is the focal length ofthe illumination electron optical system 2, and Fe is the focal lengthof each electron optical system of the elementary electron opticalsystem.

Hence, when the focal length of the illumination electron optical system2 is changed, the sizes of the plurality of intermediate images of theelectron source can be changed at the same time, and the sizes of aplurality of electron source images on the wafer 5 can also be changedat the same time. Furthermore, the elementary electron optical systemarray 3 makes the positions of the individual intermediate images differin the optical axis direction in correspondence with the curvature offield of the reduction electron optical system 4, and corrects inadvance any aberrations expected to be produced when the individualintermediate images are projected onto the wafer 5 in a reduced scale bythe reduction electron optical system 4.

The reduction electron optical system 4 comprises a symmetric magneticdoublet consisting of a first projection lens 41 (43) and secondprojection lens 42 (44). If f1 represents the focal length of the firstprojection lens 41 (43), and f2 represents the focal length of thesecond projection lens 42 (44), the distance between these two lenses isf1+f2. The object point on the optical axis AX is located at the focalpoint position of the first projection lens 41 (43), and its image pointis formed at the focal point of the second projection lens 42 (44). Thisimage is reduced to −f2/f1. Since two lens magnetic fields aredetermined to act in opposite directions, the Seidel aberrations andchromatic aberrations pertaining to rotation and magnificationtheoretically cancel each other, except for five aberrations, i.e.,spherical aberration, isotropic astigmatism, isotropic coma, curvatureof field, and on-axis chromatic aberration.

Reference numeral 6 denotes a drawing deflector for deflecting aplurality of electron beams coming from the elementary electron opticalsystem array 3 to displace a plurality of electron source images bynearly equal deflection amounts in the X- and Y-directions on the wafer5. The drawing deflector 6 comprises a main deflector 61 which has alarge deflection width but requires a long time until settlement, i.e.,a long settlement wait time, and a sub deflector 62 which has a smalldeflection width but requires only a short settlement wait time. Themain deflector 61 is an electromagnetic type deflector, and the subdeflector 62 is an electrostatic type deflector.

Reference symbol SDEF denotes a stage tracing deflector for making aplurality of electron beams coming from the elementary electron opticalsystem array 3 trace the continuous movement of the X-Y stage 12. Thestage tracing deflector SDEF comprises an electrostatic type deflector.

Reference numeral 7 denotes a dynamic focus coil that corrects anydeviations of the focus positions of the electron source images arisingfrom deflection aberration produced upon operation of the drawingdeflector 6; and 8, a dynamic stigmatic coil that corrects astigmatismof deflection aberration produced upon deflection as in the dynamicfocus coil 7.

Reference numeral 9 denotes a refocus coil for adjusting the focal pointposition of the reduction electron optical system 4 to correct blurringof electron beams due to the Coulomb effect when the number of aplurality of electron beams to be irradiated onto the wafer or the sumtotal of currents to be irradiated onto the wafer becomes large.

Reference numeral 10 denotes a Faraday cup having two single knife edgesrespectively extending in the X- and Y-directions. The Faraday cupdetects the charge amount of electron source images formed by theelectron beams coming from the elementary electron optical systems.

Reference numeral 11 denotes a θ-Z stage that carries a wafer, and ismovable in the direction of the optical axis AX (Z-axis) and in thedirection of rotation about the Z-axis. A stage reference plate 13 andthe Faraday cup 10 are fixed on the stage 11.

Reference numeral 12 denotes an X-Y stage which carries the θ-Z stageand is movable in the X- and Y-directions perpendicular to the directionof the optical axis AX (Z-axis).

FIG. 3 is a sectional view of each elementary electron optical system.

Referring to FIG. 3, a substrate AP-P is irradiated with electron beamsnearly collimated by the illumination electron optical system 2. Thesubstrate AP-P has an aperture (AP1) that defines the shape of electronbeams to be transmitted, and is common to other elementary electronoptical systems. That is, the substrate AP-P is a substrate having aplurality of apertures.

Reference numeral 301 denotes a blanking electrode which is made up of apair of electrodes and has a deflection function; and 302, a substratewhich has an aperture (AP2) larger than the aperture (AP1) and is commonto other elementary electron optical systems. On the substrate 302, theblanking electrode 301 and wiring (W) for turning on/off the electrodesare formed. That is, the substrate 302 has a plurality of apertures anda plurality of blanking electrodes.

Reference numeral 303 denotes an electron optical system, which uses twounipotential lenses 303 a and 303 b. Each unipotential lens is made upof three aperture electrodes, and has a convergence function by settingthe upper and lower electrodes at the same potential as an accelerationpotential VO, and keeping the intermediate electrode at anotherpotential V1 or V2. The individual aperture electrodes are stacked on asubstrate via insulating materials, and the substrate is common to otherelementary electron optical systems. That is, the substrate has aplurality of electron optical systems 303.

The upper, intermediate, and lower electrodes of the unipotential lens303 a and the upper and lower electrodes of the unipotential lens 303 bhave a shape shown in FIG. 4A, and the upper and lower electrodes of theunipotential lenses 303 a and 303 b are set at a common potential in allthe elementary electron optical systems by a first focal pointastigmatism control circuit 15 (to be described later).

Since the potential of the intermediate electrode of the unipotentiallens 303 a can be set by the first focal point-astigmatism controlcircuit 15 in units of elementary electron optical systems, the focallength of the unipotential lens 303 a can be set in units of elementaryelectron optical systems.

The intermediate electrode of the unipotential lens 303 b is made up offour electrodes, as shown in FIG. 4B, and the potentials of theseelectrodes can be set independently and also individually in units ofelementary electron optical systems by the first focal point-astigmatismcontrol circuit 15. Hence, the unipotential lens 303 b can havedifferent focal lengths in a section perpendicular to its optical axisand can set them individually in units of elementary electron opticalsystems.

As a consequence, by respectively controlling the potentials of theintermediate electrodes of the electron optical systems 303, theelectron optical characteristics (the intermediate image formingpositions and astigmatism) of the elementary electron optical systemscan be controlled. Upon controlling the intermediate image formingpositions, since the size of each intermediate image is determined bythe ratio between the focal lengths of the illumination electron opticalsystem 2 and each electron optical system 303, the intermediate imageforming position is moved by setting a constant focal length of eachelectron optical system 303 and moving its principal point position.With this control, the intermediate images formed by all the elementaryelectron optical systems can have nearly equal sizes and differentpositions in the optical axis direction.

Each nearly collimated electron beam output from the illuminationelectron optical system 2 forms an intermediate image of the electronsource via the aperture (AP1) and electron optical system 303. Note thatthe aperture (AP1) is located at or in the vicinity of the front-sidefocal point position of the corresponding electron optical system 303,and the blanking electrode 301 is located at or in the vicinity of theintermediate image forming position (rear-side focal point position) ofthe corresponding electron optical system 303. For this reason, if noelectric field is applied across the electrodes of the blankingelectrode 301, the electron beam is not deflected, as indicated by anelectron beam 305 in FIG. 3. On the other hand, if an electric field isapplied across the electrodes of the blanking electrode 301, theelectron beam is deflected, as indicated by an electron beam 306 in FIG.3. Since the electron beams 305 and 306 have different angledistributions on the object plane of the reduction electron opticalsystem 4, they become incident on different regions at the pupilposition (on a plane P in FIG. 19) of the reduction electron opticalsystem 4. Hence, a blanking aperture BA that transmits the electron beam305 alone is formed at the pupil position (on the plane P in FIG. 19) ofthe reduction electron optical system.

The electron lenses (electron optical systems 303) of the elementaryelectron optical systems individually set the potentials of their twointermediate electrodes so as to correct the curvature of field andastigmatism produced when the intermediate images formed thereby areprojected in a reduced scale onto the surface to be exposed by thereduction electron optical system 4, thereby making the electron opticalcharacteristics (intermediate image forming positions and astigmatism)of the elementary electron optical systems different. However, in thisembodiment, in order to decrease the number of wiring lines between theintermediate electrodes and the first focal point-astigmatism controlcircuit 15, the elementary electron optical systems included in a singlesubarray have identical electron optical characteristics, and theelectron optical characteristics (intermediate image forming positionsand astigmatism) of the elementary electron optical systems arecontrolled in units of subarrays.

Furthermore, in order to correct distortion produced when a plurality ofintermediate images are projected in a reduced scale onto the surface tobe exposed by the reduction electron optical system 4, the distortioncharacteristics of the reduction electron optical system 4 are detectedin advance, and the positions of the elementary electron optical systemsin directions perpendicular to the optical axis of the reductionelectron optical system 4 are set based on the detected characteristics.

FIG. 20 shows the system arrangement of this embodiment.

A focal length control circuit FC controls the focal length of theillumination electron optical system 2 while holding its focal pointposition on the electron source side, by adjusting the electron opticalpowers (focal lengths) of at least two of the electron lenses 2 a, 2 b,and 2 c of the illumination electron optical system 2.

A blanking control circuit 14 individually ON/OFF-controls the blankingelectrodes of the elementary electron optical systems in the elementaryelectron optical system array 3, and the first focal point astigmatismcontrol circuit 15 individually controls the electron opticalcharacteristics (intermediate image forming positions and astigmatism)of the elementary electron optical systems in the elementary electronoptical system array 3.

A second focal point astigmatism control circuit 16 controls the focalpoint position and astigmatism of the reduction electron optical system4 by controlling the dynamic stigmatic coil 8 and dynamic focus coil 7.A drawing deflection control circuit 17 controls the drawing deflector6. A stage tracing control circuit SDC controls the stage tracingdeflector SDEF to make electron beams trace the continuous movement ofthe X-Y stage 12. A magnification adjustment circuit 18 adjusts themagnification of the reduction electron optical system 4. A refocuscontrol circuit 19 adjusts the focal point position of the reductionelectron optical system 4 by controlling the currents to be supplied tothe refocus coil 9.

A stage drive control circuit 20 controls driving of the θ-Z stage, andalso controls driving of the X-Y stage 12 in collaboration with a laserinterferometer 21 that detects the position of the X-Y stage 12.

A control system 22 synchronously controls the above-mentioned controlcircuits, refocus coil 9, and Faraday cup 10 to attain exposure andalignment based on exposure control data from a memory 23. The controlsystem 22 is controlled by a CPU 25 for controlling the entire electronbeam exposure apparatus via an interface 24.

(Explanation of Operation)

Exposure of the electron beam exposure apparatus of this embodiment willbe explained below with the aid of FIG. 21.

The control system 22 directs the deflection control circuit 17 based onthe exposure control data from the memory 23 to deflect a plurality ofelectron beams from the elementary electron optical system array by thesub deflector 62 of the drawing deflector 6. Also, the control system 22directs the blanking control circuit 14 to turn on/off the blankingelectrodes of the respective elementary electron optical systems inaccordance with the pattern to be formed by exposure on the wafer 5. Atthis time, since the X-Y stage 12 is continuously moving in theX-direction, the control system 22 directs the stage tracing controlcircuit SDC to deflect the plurality of electron beams by the stagetracing deflector SDEF, so that the electron beams trace the movement ofthe X-Y stage. An electron beam coming from one elementary electronoptical system scans and exposes an exposure field (EF) on the wafer 5,as shown in FIG. 21. In this embodiment, Sx=Sy=4 μm. Since the pluralityof elementary electron optical systems of the elementary electronoptical system array are set to form their elementary exposure fields(EF) to be two-dimensionally adjacent to each other on the wafer 5, asubfield (SF) made up of a plurality of elementary exposure fields (EF)is exposed on the wafer 5 simultaneously. In this embodiment, theelementary electron optical system array 3 is configured to form an M=64(X-direction)×N=64 (Y-direction) matrix of a plurality of elementaryexposure fields (EF), and the subfield (SF) has a size of 256×256 (μm²).

The control system 22 directs the drawing deflection control circuit 17to deflect a plurality of electron beams coming from the elementaryelectron optical system array in a direction perpendicular to the stagescanning direction using the main deflector 61 of the drawing deflector6 so as to expose subfield 2 (SF2) after exposure of subfield 1 (SF1)shown in FIG. 21. Again, as described above, the control system 22directs the drawing deflection control circuit 17 to deflect a pluralityof electron beams coming from the elementary electron optical systemarray by the sub deflector 62 of the drawing deflector 6, and directsthe blanking control circuit 14 to turn on/off the blanking electrodesof the respective elementary electron optical systems in accordance withthe pattern to be formed by exposure on the wafer 5, thus exposingsubfield 2 (SF2). The subfields (SF1 to SF16) are then exposed in turn,as shown in FIG. 21, thus forming the pattern on the wafer 5. As aresult, a main field (MF) made up of subfields (SF1 to SF16) aligned ina direction perpendicular to the stage scanning direction is exposed onthe wafer 5. In this case, a line of L=16 subfields (SF) is formed inthe Y-direction, and the main field (MF) has a size of 256×4,096 (μm²).

After exposure of main field 1 (MF1) shown in FIG. 21, the controlsystem 22 directs the drawing deflection control circuit 17 to deflect aplurality of electron beams coming from the elementary electron opticalsystem array in turn to each of main fields (MF2, MF3, MF4, . . . )aligned in the stage scanning direction, thereby forming patterns on thewafer 5 by exposure.

More specifically, the electron beam exposure apparatus of thisembodiment deflects a plurality of electron beams on the wafer whilecontinuously moving the stage that carries the wafer, and individuallyON/OFF-controls the electron beams in units of deflection positions,thereby drawing a subfield made up of a plurality of elementary exposurefields by drawing patterns on the elementary exposure fields in units ofelectron beams, drawing a main field made up of a plurality of subfieldsby sequentially drawing the subfields aligned in a directionperpendicular to the continuous moving direction, and sequentiallydrawing a plurality of main fields aligned in the continuous movingdirection.

(Explanation of Generation of Exposure Control Data)

The method of generating exposure control data of the electron beamexposure apparatus of this embodiment will be explained below.

Upon reception of pattern data to be formed by exposure on the wafer,the CPU 25 executes processing for generating exposure control data, asshown in FIG. 22.

The respective steps will be described.

(Step S501)

The input pattern data is segmented into data in units of main fieldsdefined by the electron beam exposure apparatus of this embodiment.

(Step S502)

A main field to be exposed first in exposure is selected.

(Step S503)

The pattern data of the selected main field is segmented into data inunits of subfields defined by the electron beam exposure apparatus ofthis embodiment.

(Step S504)

One subfield is selected.

(Step S505)

Feature information (e.g., the minimum line width, type of line width,shape) of a pattern is detected from the pattern data of the selectedsubfield. In this embodiment, the minimum line width is detected.

(Step S506)

The minimum deflection width and electron beam diameter (the size of anelectron source image to be imaged on the wafer) that the sub deflector62 gives to an electron beam are determined based on the detectedpattern information. In this embodiment, the minimum deflection width isdetermined so that an integer multiple of the minimum deflection widthagrees with the matrix pitch (on the wafer) of a plurality of electronbeams and approximately ¼ the minimum line width. Also, the electronbeam diameter is determined to be nearly equal to that of acircumscribed circle of a square having one side equal to the minimumdeflection width.

(Step S507)

A deflection position (reference position) defined by the main deflector61 upon exposing the selected subfield is determined.

(Step S508)

The pattern data of the selected subfield is segmented into pattern datain units of elementary exposure fields corresponding to the elementaryelectron optical systems, and a common matrix made up of matrix elementsFME using the determined minimum deflection amount of the sub deflector62 as a matrix spacing is set, thus converting the pattern data intothose expressed on the common matrix in units of elementary electronoptical systems. The processing pertaining to pattern data upon exposureusing two elementary electron optical systems a and b will be describedbelow for the sake of simplicity.

FIGS. 10A and 10B show patterns Pa and Pb to be formed by exposure bythe neighboring elementary electron optical systems a and b on a commondeflection matrix DM. Each elementary electron optical system irradiatesan electron beam onto the wafer by turning off its blanking electrode athatched matrix positions with pattern portions. For this purpose, theCPU 25 determines first regions FF (solid black portions) consisting ofmatrix positions corresponding to exposure positions of at least one ofthe elementary electron optical systems a and b, and second regions NN(blank portions) consisting of matrix positions when neither of theelementary electron optical systems a and b commonly performs exposure,as show in FIG. 10C, on the basis of the matrix position data to beexposed in units of elementary electron optical systems shown in FIGS.10A and 10B. When a plurality of electron beams are located on the firstregion FF on the matrix, exposure is done by deflecting and settling theelectron beams by the deflector 6 in units of minimum deflection amounts(the matrix spacings), thus forming all the patterns to be drawn on thewafer by exposure. When a plurality of electron beams are located on thesecond region NN on the matrix, they are deflected without settlingtheir positions, thereby attaining exposure while eliminatingunnecessary deflection of the electron beams and unnecessary controldata. In other words, after exposure of the first region (FF), when theelectron beams are deflected to expose the next first region (FF) whileskipping the second region (NN), the number of times of deflection thatrequires a long settling time can be reduced, and exposure can beattained within a shorter period of time. Subsequently, the CPU 25determines the matrix positions of matrix elements to be exposed on thebasis of data pertaining to the regions FF and NN shown in FIG. 10C.Also, the CPU 25 determines the ON/OFF patterns of blanking electrodescorresponding to the matrix positions to be settled of the electronbeams in units of elementary electron optical systems on the basis ofdata representing the patterns shown in FIGS. 10A and 10B. Since theminimum deflection width and the deflection order in that matrix havealready been determined, and matrix numbers are assigned in advance tothe respective matrix elements, the matrix numbers are determined be thematrix positions.

(Step S509)

The number of settling positions (the number of times of settlement) andthe maximum deflection width from one settling position to the next oneof the sub deflector 62 are detected from the data obtained in stepS508.

(Step S510)

The exposure time for the selected subfield is calculated. Thedeflection cycle of the sub deflector 62 upon exposing the subfield isconstant, and if Ts (sec) represents the settling time of the electronbeam at the deflection position (so-called exposure time), and Torepresents the maximum settling wait time in the subfield until theelectron beam is deflected and settles to a desired deflection position,the deflection cycle Td (sec) of the sub deflector 62 is given byTd=Ts+To. The settling wait time becomes longer as the deflection widthis larger. Hence, in this step, the settling wait time To upon exposingthe subfield based on the detected maximum deflection width is obtainedbased on the relationship between the maximum deflection width andsettling wait time, which is obtained by, e.g., experiments, and thedeflection cycle Td (sec) is then calculated. The exposure time Tsub ofthe selected subfield is calculated by the equation below based on thedetected number N of settling positions:

Tsub=Td×N.

(Step S511)

It is checked if the processing in steps S505 to S510 is complete forall the subfields in the selected main field. If non-processed subfieldsremain, the flow returns to step S504 to select the next non-processedsubfield; otherwise, the flow advances to step S512.

(Step S512)

The exposure times of the subfields in the selected main field are addedto each other to calculate the exposure time of the selected main field.

(Step 5513)

The moving velocity of the stage upon exposing each main field isdetermined on the basis of the calculated exposure time of each mainfield. FIG. 23A shows an example of the relationship between the mainfields (MF(N)) and exposure times (T(n)). As shown in FIG. 23A, when theminimum deflection width is switched based on the pattern data of thecorresponding main field in units of main fields upon exposing aplurality of main fields, the exposure times of the main fields areoften different from each other. Hence, in this embodiment, the movingvelocity (V(n)) of the X-Y stage 12 is determined to be inverselyproportional to the exposure time. For example, since the width (LMF) ofthe main field in the moving direction of the X-Y stage 12 is 256 μm, ifthe exposure time T(n)=2.56 ms, the stage moving velocity V(n)=100 mm/s(=LMF/T(n)). FIG. 23B shows this relationship between the main fieldsand stage moving velocities. As described above, since exposure is doneat the stage moving velocity for each main field in accordance with theexposure time of each main field, the wafer can be exposed within ashorter period of time. This is because when the stage is controlled atequal speed like in a conventional multi-electron beam type exposureapparatus, exposure for a main field with a short exposure time can bedone within a short period of time, but exposure must be interrupteduntil the next main field moves to the deflection range of the maindeflector 61, so as to expose the next main field. However, the presentinvention does not require any interruption time.

(Step S514)

The stage moving velocity of the selected main field, the referencepositions defined by the main deflector 61, minimum deflection width,and beam diameter in units of subfields in the selected main field, thedeflection cycle of the sub deflector 62, the matrix positions definedby the sub deflector 62, and data pertaining to the ON/OFF states ofelectron beams of the elementary electron optical systems at the matrixpositions are stored.

(Step S515)

If there is a next main field, that main field is selected, and the flowreturns to step S503. If there is no main field to be exposed next uponexposure, the flow advances to step S516.

(Step S516)

Exposure control data is stored. As shown in FIG. 24, the exposurecontrol data contains, as elements, the stage moving velocities in unitsof main fields, the reference positions defined by the main deflector 61in units of subfields, the minimum deflection width of the sub deflector61, the electron beam diameter, the deflection cycle of the subdeflector 62, the matrix positions defined by the sub deflector 62, anddata pertaining to the ON/OFF states of electron beams of the elementaryelectron optical systems at the matrix positions.

In this embodiment, the above-mentioned processing steps are implementedby the CPU 25 of the electron beam exposure apparatus but may beimplemented by another processing device, and the obtained exposurecontrol data may be transferred to the CPU 25 to achieve the aboveobjective and to obtain the same effects as above.

(Explanation of Exposure Based on Exposure Control Data)

When the CPU 25 instructs the control system 22 to “execute exposure”via the interface 24, the control system 22 executes the steps shown inFIG. 25 on the basis of the exposure control data on the memory 23 inresponse to this instruction.

The individual steps will be explained below.

(Step S601)

The control system 22 directs the stage drive control circuit 20 toswitch the moving velocity of the X-Y stage 12 to that corresponding tothe main field to be exposed, thus controlling the X-Y stage 12.

(Step S602)

The control system 22 directs the drawing deflection control circuit 17to deflect a plurality of electron beams coming from the elementaryelectron optical system array to the subfield to be exposed by the maindeflector 61, so that the electron beams are located at referencepositions upon exposing the first subfield of the main field to beexposed.

(Step S603)

The control system 22 directs the focal length control circuit FC tochange the focal length of the illumination electron optical system 2,thus switching the electron beam diameter to that corresponding to thesubfield to be exposed.

(Step S604)

The control system 22 instructs the drawing deflection control circuit17 to switch the minimum deflection width of the sub deflector 61 tothat corresponding to the subfield to be exposed.

(Step S605)

The control system 22 directs the drawing deflection control circuit 17to switch the deflection cycle of the sub deflector 62 to thatcorresponding to the subfield to be exposed. Furthermore, a cycle signaldefined by the deflection cycle is generated.

(Step S606)

The control system 22 directs the drawing deflection control circuit 17to deflect a plurality of electron beams coming from the elementaryelectron optical system array by the sub deflector 62 to the deflectionpositions defined by the exposure control data in units of switchedminimum deflection widths in synchronism with the cycle signal. At thesame time, the control system 22 directs the blanking control circuit 14to turn on/off the blanking electrodes of the elementary electronoptical systems in accordance with the pattern to be formed by exposureon the wafer 5. Furthermore, in order to correct blurring of electronbeams due to the Coulomb effect, the control system 22 directs therefocus control circuit 19 to adjust the focal point position of thereduction electron optical system 4 by the refocus coil 9 on the basisof the number of electron beams to be irradiated onto the wafer withoutbeing intercepted by the blanking electrodes. At this time, the X-Ystage 12 is continuously moving in the X-direction, and the drawingdeflection control circuit 17 controls the deflection positions of theelectron beams in consideration of the moving amount of the X-Y stage12. As a result, the electron beam from each elementary electron opticalsystem scans and exposes an elementary exposure field (EF) on the wafer5, as shown in FIG. 21. Since exposure fields (EF) of the plurality ofelementary electron optical systems of the elementary electron opticalsystem array are set two-dimensionally adjacent to each other, asubfield (SF) made up of a plurality of elementary exposure fields (EF),which form a two-dimensional matrix and are exposed at the same time, isexposed on the wafer 5.

(Step S607)

If the next subfield to be exposed remains, the flow returns to stepS603; otherwise, the flow advances to step S608.

(Step S608)

If the next main field to be exposed remains, the flow returns to stepS601; otherwise, exposure is to end.

<Modification>

In the above embodiment, the stage moving velocity for each main fieldis determined to be inversely proportional to the exposure time requiredfor exposing that main field. However, when the difference between thedetermined moving velocities of neighboring main fields in thecontinuous moving direction is large, an excessive acceleration is givento the stage. As a consequence, it becomes hard to control the stage,and the position stability of the stage deteriorates. To solve thisproblem, in this modification, the higher moving velocity of neighboringmain fields is re-determined to be lower than the determined movingvelocity, so that the difference between the determined movingvelocities of neighboring main fields in the continuous moving directionbecomes equal to or smaller than a predetermined value (Vp).

This processing will be explained in detail below with reference to FIG.24.

(Step S517)

Data indicating the relationship (FIG. 23B) between the main fields andmoving velocities of the X-Y stage 12 determined in step S513 in theflow chart of FIG. 22 is input.

(Step S518)

The main field to be exposed first upon exposure is selected. Are-determination flag F is set at F=0.

(Step S519)

The difference between the moving velocity of the X-Y stage 12 uponexposing the selected main field, and that of the X-Y stage 12 uponexposing the main field to be exposed immediately before exposure of theselected main field is calculated (if there is no immediately precedingmain field, the flow jumps to step S521). If the calculated differenceis not equal to or smaller than a predetermined value (Vp) that canassure controllability and safety of the X-Y stage 12, the flow advancesto step S520; otherwise, the flow jumps to step S521.

(Step S520)

The moving velocity of the X-Y stage 12 upon exposing the main fieldcorresponding to the higher moving velocity is re-determined, so thatthe moving velocity difference becomes equal to or smaller than thepredetermined value (Vp). Also, the re-determination flag F is set atF=1.

(Step S521)

The difference between the moving velocity of the X-Y stage 12 uponexposing the selected main field, and that of the X-Y stage 12 uponexposing the main field to be exposed immediately after exposure of theselected main field is calculated (if there is no next main field, theflow jumps to step S523). If the calculated difference is not equal toor smaller than the predetermined value (Vp), the flow advances to stepS522; otherwise, the flow advances to step S523.

(Step S522)

The moving velocity upon exposing the main field corresponding to thehigher moving velocity is re-determined, so that the moving velocitydifference becomes equal to or smaller than the predetermined value(Vp).

(Step S523)

The main field to be exposed immediately after exposure of the selectedmain field is selected, and the flow returns to step S519. If there isno next main field, the flow advances to step S524.

(Step S524)

If the re-determination flag F is F=1, the flow returns to step S518. Ifthe re-determination flag F is F=0, the processing ends.

FIG. 23C shows the relationship between the main fields and stage movingvelocities obtained as a processing result of the above-mentionedprocessing shown in FIG. 26.

<Second Modification>

In this modification, as shown in FIG. 27, the exposure region on thewafer 5 is defined as follows. That is, a frame (FL1) made up of aplurality of main fields aligned in the continuous moving direction isexposed, and the X-Y stage 12 is stepped in the Y-direction. Then, thecontinuous moving direction of the X-Y stage 12 is reversed to exposethe next frame (FL2). That is, frames aligned in a directionperpendicular to the continuous moving direction of the X-Y stage 12 areexposed in turn.

In the second embodiment, the moving velocities of the X-Y stage 12 aredetermined in units of main fields. However, in this modification, themoving velocities of the X-Y stage 12 are determined in units of frames.More specifically, the moving velocity of the X-Y stage in each frame isdetermined on the basis of the longest exposure time of those of themain fields that make up the frame. Upon switching the frame to bedrawn, the moving velocity of the X-Y stage is switched to the nextdetermined velocity, and patterns are drawn by moving the X-Y stage at aconstant moving velocity in the frame.

[Explanation of a Method of Manufacturing a Device of the PresentInvention]

An embodiment of a device manufacturing method using the above-mentionedelectron beam exposure apparatus will be explained below.

FIG. 13 shows the flow in the manufacture of a microdevice (e.g.,semiconductor chips such as ICs, LSIs, liquid crystal devices, CCDs,thin film magnetic heads, micromachines, and the like). In step 1(circuit design), the circuit design of a semiconductor device is done.In step 2 (generate exposure control data), the exposure control data ofthe exposure apparatus is generated based on the designed circuitpattern. Separately, in step 3 (manufacture wafer), a wafer ismanufactured using materials such as silicon and the like. Step 4 (waferprocess) is called a pre-process, and an actual circuit is formed bylithography on the wafer using the exposure apparatus input with theprepared exposure control data, and the manufactured wafer. The nextstep 5 (assembly) is called a post-process, in which semiconductor chipsare assembled using the wafer obtained in step 4, and includes anassembly process (dicing, bonding), a packaging process (encapsulatingchips), and the like. In step 6 (inspection), inspections such asoperation tests, durability tests, and the like of semiconductor devicesassembled in step 5 are conducted. Semiconductor devices are completedvia these processes, and are delivered (step 7).

FIG. 14 shows the detailed flow of the wafer process. In step 11(oxidation), the surface of the wafer is allowed to oxidize. In step 12(CVD), an insulating film is formed on the wafer surface. In step 13(electrode formation), electrodes are formed by deposition on the wafer.In step 14 (ion implantation), ions are implanted into the wafer. Instep 15 (resist process), a photosensitive agent is applied on thewafer. In step 16 (exposure), the circuit pattern on the mask is printedon the wafer by exposure using the above-mentioned exposure apparatus.In step 17 (development), the exposed wafer is developed. In step 18(etching), a portion other than the developed resist image is removed byetching. In step 19 (remove resist), the resist film which has becomeunnecessary after the etching is removed. By repetitively executingthese steps, multiple circuit patterns are formed on the wafer.

According to the manufacturing method of this embodiment, a highlyintegrated semiconductor device which is not easy to manufacture by theconventional method can be manufactured at low cost.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention the following claims are made.

What is claimed is:
 1. An electron beam exposure apparatus for drawing apattern on an object to be exposed using a plurality of electron beams,said apparatus comprising: an electron source for emitting electrons; aplurality of elementary electron optical systems for respectivelyforming intermediate images of said electron source; a projectionelectron optical system for projecting the plurality of intermediateimages onto the object to be exposed; an illumination electron opticalsystem, which is located between said electron source and said pluralityof elementary electron optical systems, for converting the electronsemitted by said electron source into a substantially collimated electronbeam and for commonly irradiating the electron beam onto said pluralityof elementary electron optical systems; and an adjustment unit foradjusting the focal length of said illumination electron optical systemto commonly adjust sizes of the intermediate images to be projected ontothe object to be exposed.
 2. The apparatus according to claim 1, whereinsaid adjustment unit adjusts the focal length of said illuminationoptical system while fixing a focal point position of said illuminationelectron optical system on the electron source side.
 3. The apparatusaccording to claim 2, wherein said illumination electron optical systemcomprises a plurality of electron lenses disposed in an optical axisdirection, and said adjustment unit adjusts the focal length of saidillumination electron optical system while fixing the focal pointposition of said illumination electron optical system on the electronsource side, by changing focal lengths of at least two of said pluralityof electron lenses.
 4. The apparatus according to claim 2, furthercomprising an axis correction unit for correcting position deviations ofthe intermediate images to be projected onto the object to be exposed,produced when said adjustment unit adjusts the focal length of saidillumination electron optical system.
 5. The apparatus according toclaim 4, wherein said axis correction unit corrects the positiondeviations of the intermediate images of said electron source to beprojected onto the object to be exposed by correcting positions of theplurality of intermediate images formed immediately below said pluralityof elementary electron optical systems.
 6. The apparatus according toclaim 1, further comprising a scanning unit for scanning theintermediate images to be projected onto the object to be exposed, andwherein said adjustment unit dynamically adjusts a minimum scanningwidth of said scanning unit in correspondence with the sizes of the dotpatterns to be formed on the object to be exposed.
 7. The apparatusaccording to claim 6, wherein said scanning unit comprises a deflectorfor deflecting electron beams to be irradiated from said plurality ofelementary electron optical systems onto the object to be exposed, andsaid adjustment unit dynamically adjusts a minimum deflection width ofsaid deflector in correspondence with the sizes of the dot patterns tobe formed on the object to be exposed.
 8. The apparatus according toclaim 7, wherein said adjustment unit dynamically adjusts a deflectioncycle of said scanning unit in correspondence with the minimumdeflection width of said deflector.
 9. The apparatus according to claim6, wherein said adjustment unit dynamically adjusts a scanning cycle ofsaid scanning unit in correspondence with the minimum scanning width ofsaid scanning unit.
 10. The apparatus according to claim 1, wherein saidplurality of elementary electron optical systems have a function ofcorrecting any aberrations produced upon projecting the plurality ofintermediate images formed by said plurality of elementary electronoptical systems onto the object to be exposed via said projectionelectron optical system.
 11. The apparatus according to claim 1, whereinsaid adjustment unit dynamically adjusts the sizes of the dot patternsto be formed on the object to be exposed by projecting the intermediateimages in accordance with a unit exposure field to be exposed of theentire field of the pattern to be drawn by exposure on the object to beexposed, the entire field being made up of a set of a plurality of unitexposure fields.
 12. The apparatus according to claim 11, wherein saidadjustment unit adjusts the sizes of the dot patterns to be formed onthe object to be exposed by projecting the intermediate images in unitsof unit exposure fields on the basis of a feature of an exposure patternin the corresponding unit exposure field.
 13. The apparatus according toclaim 11, wherein said adjustment unit adjusts the sizes of the dotpatterns to be formed on the object to be exposed by projecting theintermediate images in units of unit exposure fields on the basis of aminimum line width of an exposure pattern in the corresponding unitexposure field.
 14. An apparatus for generating exposure control dataused for controlling an electron beam exposure apparatus of claim
 1. 15.A method of controlling an electron beam exposure apparatus, which hasan electron source for emitting electrons, a plurality of elementaryelectron optical systems for respectively forming intermediate images ofsaid electron source, a projection electron optical system forprojecting the plurality of intermediate images onto the object to beexposed, and an illumination electron optical system, which is locatedbetween said electron source and said plurality of elementary electronoptical systems, for converting the electrons emitted by said electronsource into a substantially collimated electron beam and for commonlyirradiating the electron beam onto said plurality of elementary electronoptical systems, said method comprising the step of: adjusting the focallength of the illumination electron optical system to commonly adjustsizes of the intermediate images to be projected onto the object to beexposed.
 16. A method of generating exposure control data used forcontrolling an electron beam exposure apparatus, which has an electronsource for emitting electrons, a plurality of elementary electronoptical systems for respectively forming intermediate images of saidelectron source, a projection electron optical system for projecting theplurality of intermediate images onto the object to be exposed, and anillumination electron optical system, which is located between saidelectron source and said projection electron optical systems, forconverting the electrons emitted by said electron source into asubstantially collimated electron beam and for commonly irradiating theelectron beam onto said plurality of elementary electron opticalsystems, said method comprising the steps of: dividing a pattern to bedrawn by exposure on the object to be exposed into a plurality ofblocks; detecting features of patterns in the blocks; determining thefocal length of the illumination electron optical system to commonlyadjust sizes of the intermediate images to be projected onto the objectto be exposed; and generating exposure control data on the basis of thedetermination result.